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Between September 17 and 18, 2022, a series of earthquakes struck the southern Longitudinal Valley of Taiwan, causing severe damage to infrastructure, particularly bridges, railroads, buildings, and highways in Taitung and Hualien. The primary event in this sequence was the Chihshang earthquake, measuring magnitude of M L 6.9, preceded by a significant foreshock of M L 6.4 the day before. Notably, the highest intensity reported in the epicentral region during this earthquake sequence reached 6 + , marking the highest intensity ever recorded since the Central Weather Bureau (CWB) revised its seismic intensity scale. In this study, we examined the strong ground motion data recorded by the low-cost P-alert network to investigate the cause of structural damage to buildings, railway stations, schools, and other structures in the affected area. Our analysis encompassed data from a total of 17 monitoring stations. The observed peak ground acceleration (PGA) ranges from 0.06 g and 0.78 g, the peak spectral acceleration or response spectrum (PSA) spanned from 0.20 g at 0.50 s to 3.87 g at 0.41 s, and site amplification varied from 4 at 0.6 Hz to 12.6 at 5.2 Hz. The reported damage of single storey house at Taitung City is correlated with the higher amplification 4.5 at 0.14 s; Bridge and factory at Chihshang Township is correlated with the higher amplification 5 at 0.17 s; Railway station at Zhuoxi Township with the higher amplification 7.5 at 0.3 s; of three storey building at Yuli Township with amplification 8 at 0.26 s and, also higher PSA 2.83 g at 0.29 s, and several schools at Kaoshiung City with amplification 7.2 at 0.37 s and with high PSA 3.87 g at 0.41 s. Additionally, we studied the static Coulomb stress changes resulting from the coseismic slip of the main shock, which contributed to an increase in aftershock occurrences. The occurrence of a high-intensity earthquake ( M L 6.9) on September 18, 2022, within a region of positive Coulomb stress changes, provides support for the hypothesis of aftershock triggering. Through analysis, we found that stronger foreshock ( M L 6.4) occurred in the rupture area of mainshock foreshock, positioned adjacent to the main fault. [ABSTRACT FROM AUTHOR]

The cumulative absolute absement (CAA) of the 3 s window after P-wave arrival can be used to estimate the magnitude ( M CAA ) of an earthquake. This method can achieve good results even when only the six stations nearest to the epicenter are used. The standard deviation between the estimated CAA magnitude ( M CAA ) and the moment magnitude ( M w ) is found to be 0.3 when using either 6 or 20 stations. This means that M CAA can be reliably predicted using the closest 6 stations. On the other hand, the magnitude ( M Pd ) derived from P d using the closest 20 stations has a standard deviation of 0.4 between the estimated M Pd and M w . This suggests that CAA is a better magnitude determination parameter for the EEW system than P d . [ABSTRACT FROM AUTHOR]

Building an earthquake early warning (EEW) network requires the installation of seismic instruments around the seismogenic zone. Using low-cost sensors to build a seismic network for EEW and to generate shakemaps is a cost-effective way in the field of seismology. The National Taiwan University (NTU) network employing 762 P-Alert low-cost sensors based on micro-electro-mechanical systems (MEMS) technology is operational for almost the last 10 years in Taiwan. This instrumentation is capable of recording the strong ground motions of up to ± 2 g and is dense enough to record the near-field ground motion. The NTU system has shown its importance during various earthquakes that caused damage in Taiwan. Although the system is capable of acting as a regional as well as an onsite warning system, it is particularly useful for onsite warning. Using real-time seismic signals, each P-Alert device provided a 2–8 s warning time for the near-source earthquake regions situated in the blind zone of the Central Weather Bureau (CWB) regional EEW system, during the 2016 M w 6.4 Meinong and 2018 M w 6.4 Hualien earthquakes. The shakemaps plotted by the P-Alert dense network help to assess the damage pattern and act as key features in the risk mitigation process. These shakemaps are delivered to the intended users, including the disaster mitigation authorities, for possible relief purposes. Currently, the P-Alert network can provide peak ground acceleration (PGA), peak ground velocity (PGV), spectral acceleration ( S a ) at different periods, and CWB intensity shakemaps. Using shakemaps, it is found that PGV is a better indicator of damage detection than PGA. Encouraged by the performance of the P-Alert network, more instruments are installed in Asia-Pacific countries. [ABSTRACT FROM AUTHOR]

Geodetic evidence for slow slip recurrence changed by stress perturbations was rare, especially from afterslip following a nearby large earthquake. The first observed slow slip events in the southernmost Ryukyu subduction had occurred in 2005, 2009, and 2015 following the nearby 2002 March 31 Mw 7.1 Hualien offshore earthquake. To investigate whether the Mw 7.1 earthquake had influenced the occurrence times of the slow slip, we calculated the coseismic slip distribution and afterslip distribution using the surface displacements from onshore Global Navigation Satellite System observations. The stress perturbation on the slow-slip regions caused by the coseismic slip was quantified using the Coulomb failure criteria. We also examined the aftershock distribution and the evolution with time to clarify the stress perturbations from the afterslip offshore. Our results show that the primary afterslip distribution may have overlapped the 2009 and 2015 slow-slip patch at the downdip of the earthquake. The coseismic stress perturbation may have influenced the SSEs area directly by a Coulomb stress increase of probably 0.10 MPa. However, the 2005 SSE patch in the updip depths had only a little coseismic slip and afterslip with the Coulomb stress increase of approximately 0.06 MPa. We find that most of the aftershocks had occurred in the 2009 and 2015 slow-slip region that evolved into a typical aftershock sequence at least 2.5 years after the earthquake. The surface geodetic displacements reveal that the afterslip may have lasted longer than 4.5 years after the earthquake. The evidence for the afterslip proves that the 2009 and 2015 slow-slip patch was influenced by the afterslip directly for years. We suggest that the ongoing afterslip may have modulated the coseismic stress perturbation. It may explain the delay of the 2009 slow slip occurrence compared with the recurrence interval between the 2009 and 2015 slow slip events. [ABSTRACT FROM AUTHOR]

The earthquake early warning (EEW) system in Taiwan is the outcome of rigorous research work carried out at various levels after the occurrence of the 1986 Hualien earthquake that caused destruction. After more than 25 years of development, three different EEW systems exist in Taiwan. Currently, the nation wide regional EEW system is operated by the Central Weather Bureau (CWB), whereas, a hybrid (regional & onsite) system based on Micro-Electro-Mechanical System sensors is run by National Taiwan University (NTU). The third EEW (onsite system) is run by the National Center for Research on Earthquake Engineering (NCREE). Both CWB and NTU systems are capable of reporting the EEW warnings within 20 seconds of earthquake occurrence. The CWB system is incharge of providing earthquake alerts in Taiwan via text message through mobile phone, TV, and directly broadcasting system to schools and is providing earthquake alarms to the general public since 2016. During recently damaging earthquakes in Taiwan, the NTU system provided 2–8 seconds onsite warning (lead time) in the blind zone around the epicenter. The NTU system also can generate near real-time shake maps for rapid response purposes. The NCREE system consists of about 98 stations and can provide several seconds lead time in the area near the epicenter. The NCREE system also can receive CWB regional EEW messages for warning the regions away from the epicenter. Individually every system has its advantage, however, the hybrid approach will be one of the future systems for real operation. [ABSTRACT FROM AUTHOR]

The local magnitude scale ML is defined by the difference between the observed amplitude (log A ) and the anchored attenuation amplitude (log A 0 ). A previous study in Taiwan established a model of the anchored amplitude as a function of the hypocentral distance R by matching the ML to the corresponding moment magnitude MW. Although the overall performance of the model is adequate, there remain some drawbacks, namely, the correlated empirical station correction problem and relatively low sample size. In this paper, we adopt the concept of the expectation-maximization (EM) algorithm to develop a new method that can simultaneously estimate the anchored amplitude model coefficients and station corrections. The revised catalog using the latest dataset in Taiwan provides an up-to-date accurate estimate of ML. Additionally, the proposed method can systematically obtain statistically meaningful results and be applied to datasets of other regions in the future. [ABSTRACT FROM AUTHOR]

Moment tensor decomposition is a method for deriving the isotropic (ISO), double-couple (DC), and compensated linear vector dipole (CLVD) components from a seismic moment tensor. Currently, there are two families of methods, namely, standard moment tensor decomposition and Euclidean moment tensor decomposition. Although both methods can usually provide workable solutions, there are some minor inconsistencies between the two methods: an equality inconsistency that occurs in standard moment tensor decomposition and the pure CLVD unity and flip basis inconsistency encountered in Euclidean moment tensor decomposition. Moreover, there is a sign problem when disentangling the CLVD component from a DC-dominated case. To address these minor inconsistencies, we propose a new moment tensor decomposition method inspired by both previous methods. The new method can not only avoid all these minor inconsistencies but also withstand deviations in ISO- or CLVD-dominated cases when using source-type diagrams. [ABSTRACT FROM AUTHOR]

A sequence of eruptions in the lower East Rift Zone (LERZ) of the Kilauea, Hawaii volcano commenced in early May 2018 and caused serious damage and residential evacuation. The post-eruption drainage and collapses of the summit lava lake and caldera suggest a well-connected magmatic plumbing system along the rift zone. How and when the pre-eruptive magmatic processes in such connecting system occurred are, however, still unclear. For that, we apply ambient noise interferometry with seismic data from January 2017 to June 2018 from 12 broadband seismometers to investigate spatiotemporal seismic velocity changes (dv/v) of the upper crust in the Kilauea area. The dv/v variations in three frequency bands (0.3–0.6 Hz, 0.6–0.9 Hz, and 0.9–2.0 Hz) show distinct responses to strong earthquake ground shaking and deep magmatic intrusion processes. Earthquake-induced dv/v drops mainly in the higher two frequency bands imply shallow mechanical changes within the uppermost 1 km of the crust. In contrast, the magma-related dv/v changes can be characterized into three periods of activity: from the December 2017 to March 15, 2018, a dv/v excursion only seen in the lowest frequency band indicates the magmatic intrusion processes taking place at the depth range of 1–4 km, consistent with the proposed depth of the magma reservoir-dike system in the rift zone. The spatial dv/v distribution suggests that the magma may intrude to the deeper summit magma reservoir and in the upper East Rift Zone (UERZ) at this time. From March 15 to April 17 in 2018, the summit inflation recorded by tiltmeters causes the dv/v increases in the higher two frequency bands. After April 17 to the eruption, the accumulating damage of the edifice together with the stronger intrusion activity in the UERZ result in dv/v decreases in all three frequency bands around the summit and UERZ areas. Our observations highlight that the ambient noise interferometry analysis provides an opportunity to image and understand the pre-eruptive processes of reservoir-dike magma system and could be a useful supplement to current volcanic monitoring systems. [ABSTRACT FROM AUTHOR]

Uttarakhand Himalayas are highly sensitive to seismic hazard with possible occurrence of high-magnitude earthquakes. Fewer waveforms are available from previously recorded earthquakes, which are insufficient for carrying out seismic hazard studies. The recently installed strong motion instrumentation network (SMIN) in India, particularly, in Indian Himalayas is providing useful data. Using recorded data from SMIN, time-dependent peak ground acceleration and observed peak ground velocity shake maps are drawn for two earthquakes widely recorded by SMIN in Uttarakhand region of Indian Himalayan belt. Open-source Earthworm software with new algorithms is used for drawing these shake maps. The source mechanism is computed for April 4, 2011 earthquake using waveform inversion technique to relate it to the trend of shake maps. The computed focal mechanism shows one of the nodal planes in NW–SE, which are consistent with shake maps for the same earthquake. These time-dependent plotted shake maps provide useful information on the initial rupture, as well as the potential directivity of the rupture. [ABSTRACT FROM AUTHOR]

The main goal of present study is to test the functionality of an earthquake early warning (EEW) system (a life-saving tool), in India using synthesized data and recorded earthquake data from Taiwan. In recent time, India set up an EEW system in the central seismic gap along the Himalayan Belt, consisting of about 100 low-cost P-Alert instruments. The area, where these instruments are installed, is highly sensitive to the seismic risk with the potential of strong, major and great earthquakes. In the absence of recorded data from the Himalayas required for analysis of such system, we take advantage of recorded waveforms from Taiwan, to test the EEW system. We selected Taiwanese stations in good accordance with the Indian sensor network, to have a best fit in terms of inter station spacing. Finally, the recorded waveforms are passed through Earthworm software using tankplayer module. The system performs very well in terms of earthquake detection, P-wave picking, earthquake magnitude and location (using previously estimated regressions). Pd algorithm has been tested where the peak amplitude of vertical displacement is used for estimating magnitudes using previously regressed empirical relationship data. For the earthquakes located between Main Boundary Thrust and Main Central Thrust along with a matching instrumentation window, a good estimate of location, as well as magnitude is observed. The approach based on Pd for estimating magnitude works perfectly as compared to τc approach, which is more sensitive to signal-to-noise ratio. To make it more region specific, we generated synthetic seismograms from the epicenters of historical Chamoli (1999) and Uttarkashi (1991) earthquakes at EEW stations in India and checked the functionality of EEW. While placing these earthquakes within the instrumentation window, a good approximation of earthquake location and magnitude is obtained by passing these generated waveforms. The parameters used to judge the performance of EEW system included the time taken by the system in issuing warning after the confirmation of the occurrence of damaging earthquake and the lead time (time interval between the issuing of warning and arrival of damaging earthquake ground motion at a particular location). High lead times have been obtained for the plainer regions including thickly populated regions of Gangetic plains, such as Delhi National Capital Region according to the distance from the epicenter, which are the main target of EEW system. [ABSTRACT FROM AUTHOR]

In present work, seismic hazard from future earthquake is worked out for Delhi region in terms of different strong motion parameters such as peak ground acceleration (PGA), characteristics frequency and spectral acceleration (Sa). The earthquake of March 5, 2012, is taken as key earthquake for synthesis. Stochastic finite modeling technique based on dynamic corner frequency initially is used to produce and match the ground motion histories where 2012 earthquake was recorded. The matching is attained in terms of PGA, response spectra and duration. Once a good match is found, the ground motion is estimated for higher magnitude earthquakes (i.e., Mw 6.0 and Mw 6.5). Our work demonstrates that a Mw 6.0 magnitude earthquake in proximity of Delhi will deliver PGA estimations of 20-209 gal (1 cm/s = 1 gal), the lower values occurring at hard rock sites like NDI (IMD) and DJB. Similarly Mw 6.5 earthquake may produce PGA values ranging between 30 and 323 gal. Finally seismic hazard in Delhi and surrounding regions is estimated from Mw 6.5 magnitude earthquake in terms of PGA, Sa and predominant period. Our computation specifies that at short period, the small structures toward eastern and north-western part of Delhi city may be affected by the earthquakes. For a case of 0.5 s period, Sa values are distributed uniformly at all the places in Delhi, indicating that the buildings with five floors or so may be in danger from future higher magnitude earthquakes. The Sa maps acquired in this study can be utilized to survey the seismic danger of the region and identify vulnerably susceptible areas in and around Delhi from future higher magnitude earthquake. [ABSTRACT FROM AUTHOR]

In the present work, ground motion is estimated from future scenario earthquakes at different sites in Uttarakhand Himalayas in India using empirical Green's function (EGF) technique. The recorded ground motion from April 4, 2011, M 5.4 earthquake is taken as a basic element. The ground motion is estimated at 24 sites, where the element earthquake was recorded. It is observed from synthesized time histories that sites located near the epicenter may expect accelerations in excess of 1 g. In the present analysis, Dharchula can expect ground accelerations in excess of 1 g. For M 7.0, the expected peak values of acceleration ( A ) and velocity ( V ) on horizontal components at different sites range between 11 and 912 gal and 5 and 52 cm/s, respectively. The corresponding values for the Z component range between 8 and 228 gal, and 3 and 14 cm/s, respectively. Similarly, for M 7.5, the expected A and V on horizontal components at different sites range between 25 and 1281 gal and 25 and 102 cm/s, respectively. The corresponding values for the Z component range between 14 to 474 gal, and 15 to 70 cm/s, respectively. The site amplification functions are estimated using the horizontal-to-vertical spectral ratio procedure. Zone IV (on a scale of II to V according to the seismic zonation map for India) response spectrum for 5 % damping is deficient for M 7.0, while zone V response spectrum is exceeded at several frequencies for same magnitude. For M 7.5, zone IV response spectrum is conservative (except at some frequencies), while zone V response spectrum is exceeded at many sites. The estimated PGA values can be incorporated in marking the weak areas in the central Himalaya, thereby assisting the designing and construction of new structures. [ABSTRACT FROM AUTHOR]

Taiwan is one of the leading developers of earthquake early warning (EEW) systems. The Central Weather Bureau has been the primary developer of the EEW system in Taiwan since 1993. In 2010, the National Taiwan University (NTU) developed an EEW system for research purposes using low-cost accelerometers. As of 2014, a total of 506 stations have been deployed and configured. The NTU system can provide earthquake information within 15 s of an earthquake occurrence. Thus, this system may provide early warnings for cities located more than 50 km from the epicenter. Additionally, the NTU system also has an onsite alert function that triggers a warning for incoming P-waves greater than a certain magnitude threshold, thus providing a 2-3 s lead time before peak ground acceleration for regions close to an epicenter. Detailed shaking maps are produced by the NTU system within one or two minutes after an earthquake. Regions of high shaking indicated by the shalking map can indicate locations of damage and casualties and help estimate the damage incurred. The direction of earthquake ruptures are also potentially identified based on detailed shaking maps and strong motion records of the NTU system. [ABSTRACT FROM AUTHOR]

Since the year 1973, more than 54,000 M ≥ 3.0 earthquakes have occurred around Taiwan, and their magnitude-frequency relationship was found following with the Gutenberg-Richter recurrence law with b value equal to 0.923 from the least-square calculation. However, using this b value with the McGuire-Arabasz algorithm results in some disagreement between observations and expectations in magnitude probability. This study introduces a simple approach to optimize the b value for better modeling of the magnitude probability, and its effectiveness is demonstrated in this paper. The result shows that the optimal b value can better model the observed magnitude distribution, compared with two customary methods. For example, given magnitude threshold = 5.0 and maximum magnitude = 8.0, the optimal b value of 0.835 is better than 0.923 from the least-square calculation and 0.913 from maximum likelihood estimation for simulating the earthquake's magnitude probability distribution around Taiwan. [ABSTRACT FROM AUTHOR]

Statistical studies on earthquake recurrence time probabilities have frequently been applied to seismic hazard analyses. In Taiwan, an instrumental catalog provides a good opportunity to examine statistical attributes of earthquakes around the study region, with the objective to evaluate the seismic risk and earthquake potential for hazard mitigation. With the completeness of recordings, seismic rates for small-to-moderate magnitudes can be obtained. An elimination of aftershocks was performed using a double-link cluster analysis method. The time intervals between a series of events (the inter-occurrence periods) are stationary with an identical temporal distribution. Based on the goodness-of-fit testing between a few models and observation, we suggested the use of the Gamma distribution in modeling this variable, earthquake inter-occurrence periods, for the study region. Accordingly, unified relationship was constructed, and statistical limitations of sparse sampling for devastating earthquakes (such as M ≥ 6.0 or 7.0) could be resolved. The empirical result evaluated by introducing the conditional probability indicates that the recurrence probability of a M ≥ 7.0 earthquake is 78.8 % within 10 years in Taiwan region. [ABSTRACT FROM AUTHOR]

This study first presents the series of peak ground acceleration (PGA) in the three major cities in Taiwan. The PGAs are back-calculated from an earthquake catalog with the use of ground motion models. The maximums of the 84th percentile (mean + one standard deviation) PGA since 1900 are 1.03, 0.36, and 0.10 g, in Taipei, Taichung, and Kaohsiung, respectively. Statistical goodness-of-fit testing shows that the series of PGA follow a double-lognormal distribution. Using the verified probability distribution, a probabilistic analysis was developed in this paper, and used to evaluate probability-based seismic hazard. Accordingly, given a PGA equal to 0.5 g, the annual exceedance probabilities are 0.56, 0.46, and 0.23 % in Taipei, Taichung, and Kaohsiung, respectively; for PGA equal to 1.0 g, the probabilities become 0.18, 0.14, and 0.09 %. As a result, this analysis indicates the city in South Taiwan is associated with relatively lower seismic hazard, compared with those in Central and North Taiwan. [ABSTRACT FROM AUTHOR]

The annual maximum earthquake magnitudes around Taiwan from 1900 to 2009 are presented in this paper. Using the distribution of the AMEM, a probabilistic framework to estimate the recurrence probability of a large-size earthquake is also proposed and an illustration was made in this paper. The mean value of the 110-AMEM is 6.433, and the coefficient of variation is around 10%. The results of two goodness-of-fit tests show that the Gamma and lognormal distributions are relatively suitable to represent the AMEM around Taiwan among five common probability distributions. Using the proposed approach, the recurrence probability is 4% for an earthquake with magnitude greater than 7.5 in a 1-year period around Taiwan. More site-specifically, the probability is around 5% in Central Taiwan for such an earthquake to occur in a 50-year period. [ABSTRACT FROM AUTHOR]

A transition and subduction zone adjacent to the Ryukyu Arc, Ryukyu Trench, and Okinawa Trough, extends between southern Japan and northeastern Taiwan. It is generated during the northwestward subduction of the Philippine Sea Plate, which lies the Eurasian Plate along the Ryukyu Trench. The movement of the Philippine Sea Plate is hindered at the northeastern corner of Taiwan, which causes complicated structure of the Philippine Sea Plate at the western end of the Ryukyu subduction zone. Development of the active subduction and transition boundary near the western Ryukyu Arc is evaluated statistically by using displacements derived from GPS site data. The statistical model shows that the absolute displacement derived from GPS measurements of nearly 8 years indicates a maximum spatial variation of 0.625 m. Three trends are observed for such long-term progress, and use of linear regression also reveals quite good consistency between the data and statistic models. Such rate is also elevated following the trend development. Southeastern and nearly horizontal movement is suggested to the main development of for the site movements, it is likely related to the tensional activity adjacent to this boundary. [ABSTRACT FROM AUTHOR]

A better real-time assessment of earthquake effects (i.e. seismic intensity estimation)is crucial for hazard mitigation. Especially during the aftermath of a disastrous event,significant reduction of loss can usually be realized through timely execution ofemergency response measures. These effects include strong-ground shaking, groundfailure, and their impact on man-made structures. The descriptive Modified Mercalliintensity scale, though still in common use in many poorly instrumented areas of theworld, is out of date in areas of extensive strong-motion instrumentation. It is desirableto place the earthquake intensity scale on a more quantitative basis based on the actualrecorded ground-motion shaking and carefully compiled damage records. In this paper,we investigated the relationships between earthquake loss, intensity and strong motionpeak values, mainly based on the Chi-Chi earthquake. Both the strong-motion peakvalues and the earthquake loss are related. From the results, we found that peak groundacceleration (PGA) and peak acceleration response spectra at 1 s period (1 s Sa) valuesare two parameters that give slightly higher correlation coefficients than other parametersfor earthquake loss analysis. For intensity estimations, the peak ground velocity (PGV)values and 1 s Sa values are better parameters in the high range and PGA is not stable forsmaller earthquakes. Although PGV values give a slightly lower correlation coefficientand larger standard deviation in seismic loss analysis during the Chi-Chi earthquake, itnevertheless gives more reliable instrumental intensity over a broad magnitude range.1 s Sa is a good parameter for both seismic losses and intensity evaluation. We thusconclude that PGV and 1 s Sa are relatively more stable in damage assessment and,at least in the high end, in intensity estimation. We shall incorporate these findings inour real-time earthquake rapid reporting and early warning systems. [ABSTRACT FROM AUTHOR]

Development of earthquake early warning system (EEWS) is in advanced stage in different parts of the world including India. The success of EEWS for mitigating seismic risk and saving human lives has been well documented in Mexico, Japan, and Taiwan, where the alert is issued to the public. Taking advantage of the recorded ground motion data from the network of Institute of Seismological Research (ISR), India, with magnitude range 3.0–5.2, we investigated correlations between various ground motion parameters like peak ground acceleration (PGA), peak ground velocity (PGV), peak ground displacement (PGD), Pa, Pv, Pd, and τc.Three- to 5-s time windows are considered to measure Pa, Pv, Pd, and τc from the vertical component of the waveforms. Linear regression analysis is performed at various time steps (3- to 5-s time interval). The results show that considering 4- and 5-s windows exhibits good relationships compared with the 3-s window, which shows more scattering. These empirical relationships using τc and M as well as Pd and M are very helpful in determining the earthquake magnitude and subsequently taking steps toward risk assessment. [ABSTRACT FROM AUTHOR]

Hazards from gravity-driven instabilities on hillslope (termed 'landquake' in this study) are an important problem facing us today. Rapid detection of landquake events is crucial for hazard mitigation and emergency response. Based on the real-time broadband data in Taiwan, we have developed a near real-time landquake monitoring system, which is a fully automatic process based on waveform inversion that yields source information (e.g., location and mechanism) and identifies the landquake source by examining waveform fitness for different types of source mechanisms. This system has been successfully tested offline using seismic records during the passage of the 2009 Typhoon Morakot in Taiwan and has been in online operation during the typhoon season in 2015. In practice, certain levels of station coverage (station gap < 180°), signal-to-noise ratio (SNR ≥ 5.0), and a threshold of event size (volume >106 m3 and area > 0.20 km2) are required to ensure good performance (fitness > 0.6 for successful source identification) of the system, which can be readily implemented in other places in the world with real-time seismic networks and high landquake activities. [ABSTRACT FROM AUTHOR]

A correction to the article "Potential volume for CO2 deep ocean sequestration" that was published on November 25, 2015, on assessment of the area located in the western Pacific Ocean, is presented.

Continuous seismic records near river channels can be used to quantify the energy induced by river sediment transport. During the 2011 typhoon season, we deployed a seismic array along the Chishan River in the mountain area of southern Taiwan, where there is strong variability in water discharge and high sedimentation rates. We observe hysteresis in the high-frequency (5-15 Hz) seismic noise level relative to the associated hydrological parameters. In addition, our seismic noise analysis reveals an asymmetry and a high coherence in noise cross-correlation functions for several station pairs during the typhoon passage, which corresponds to sediment particles and turbulent flows impacting along the riverbed where the river bends sharply. Based on spectral characteristics of the seismic records, we also detected 20 landslide/debris flow events, which we use to estimate the sediment supply. Comparison of sediment flux between seismologically determined bedload and derived suspended load indicates temporal changes in the sediment flux ratio, which imply a complex transition process from the bedload regime to the suspension regime between typhoon passage and off-typhoon periods. Our study demonstrates the possibility of seismologically monitoring river bedload transport, thus providing valuable additional information for studying fluvial bedrock erosion and mountain landscape evolution. [ABSTRACT FROM AUTHOR]